Series v parallel solar panels.

[Zonker]

Originally Posted by noelex 77

The maximum power point changes with changing conditions. The "T" in MPPT stands for tracking. The input voltage to the controller is constantly adjusted to maximise the output of the solar panel. This is one of the major functions of a MPPT controller. I don’t see how your system achieves this.

This setup is ok for a "ONE" panel and "ONE" MPPT controller setup.


But not on a boat with multiple panels which all deliver different wattage due to shading and/or heeling.


Take the MPPT controller apart and then you understand what my point is.

[wholybee]

Originally Posted by wholybee

What happens as the insolation decreases? Walk through it, what happens to the voltage and current from the panels?

Originally Posted by Zonker

As I said you have no clue about EE ...

Is that so?

Panel producing 20W @ 20V.


1) totally shaded -> 0W => what is the voltage achievable
2) partially shaded -> 10W => how much current can "a regulator" deliver @ 40V


-> this is at high school level ...

So walk me through it then. Prove you know what you are talking about. What happens throughout the system as insolation decreases?

So what if we have a MPPT for each panel and all MPPTs going to the same battery bank -> kinda gets difficult since the sensors which affect each other.

So what is the cheap solution to avoid the issues with multiple panels and multiple MPPT controllers ...


Yea ... some ppl read and learn, some ppl just throw bs.

All I am getting from you is BS. If you can't explain it, you don't understand it. EE or not.

[barnakiel]

Originally Posted by smac999

A 12v panel means it works on a 12v battery with a pwm controller. Which means the panel is 20v. But that wording isn’t really used anymore since now everyone uses mppts.

You just glided over the fact that some very popular mppt controllers, do not kick in before the voltage is say 5V above the battery, now in some scenarios it takes quite some time before the a 12V panel gets to 18V.


You are hearing this from someone who sailed long miles out of Gran Canaria wondering why the hell my new Victron mppt regulator does not work for like an hour after sunrise. Switched back to pwm and BOOM here we have the power.


Sure thing, I was smart enough (after some reading) to re wire our panels in series, making them a 24 panel. And now HEY HEY now it worked.


So to say, mppt is a cool toy, but shifting from pwm to mppt has its own set of traps.


BTW I have measured a Victron mppt and a Chinois pwm head to head on two panelss side by side and on the same batter - and the cheapo Chinoise thing harvested about 5% more juice - Martinique sun. Yes I did switch the panels next day and the result was less - maybe 2%. And yet.


So I do have my arguments against some mppt (namely : Victrons) to put them between a 12V panel, in a 12V battery system. Now that I am using 24V panels onto 12V battery, with the same Victron regulator - and it works great.


Capenejszn ?


barnakiel

[donradcliffe]

Before we degenerate into chest thumping, I have a geek question.

If the PWM and MPPT controllers control charging by cutting the width of constant voltage pulses, and LiFePo4 battery life is affected by charging voltage, has anyone done a study on the effects of the PWM and MPPT on battery life? In other words, do those short 20v pulses damage your batteries?

I have a friend who is a VERY smart geek (he writes RV design and repair books), and after I convinced him to dump lead acid and go to LiFePo4, he put together a massive system for his RV which uses parallel panels mercury switches (like the really old solar controllers) to keep his bank charging between a cut in and cut out voltage. He's been running his system for a couple of years now, and loves the LiFePo4.

[wholybee]

That's not really what happens with MPPT though. It is only 20V(or whatever high voltage) pulses internally and with no load. There is an LC filter in the MPPT controller to convert the pulses to a constant voltage. See this schematic, L1 and the 3 capacitors just to the right of it, at the output to the battery.

https://makingcircuits.com/blog/mppt...arger-circuit/

What your friend does would work just fine. Not as well as an MPPT, but much cheaper and simple.

[noelex 77]

Originally Posted by barnakiel

You are hearing this from someone who sailed long miles out of Gran Canaria wondering why the hell my new Victron mppt regulator does not work for like an hour after sunrise. Switched back to pwm and BOOM here we have the power.

Contrary to expectations, PWM controllers are better than MPPT controllers very early in the morning and late in the evening if the solar panel Vmp is reasonably close to the battery voltage. So your results are not surprising. This is because MPPT controllers have a high self consumption. Running all that complex circuitry and voltage conversion takes some energy.

For this reason MPPT controllers "go to sleep" when the energy available from the solar panels is likely less than their own self consumption. Periodically the controller checks the solar panel parameters and will "wake up" if certain conditions are met. The usual condition is that the solar panel voltage has to be significantly above the battery voltage. The popular Victron controllers require a solar panel voltage of 5 volts over the battery voltage before they will wake up in the morning (thereafter +1 V) The reason 5 volts is chosen is that below this number it is likely the solar panel would not be able to contribute more energy than the controller can consume. This starting voltage has been criticised by some (including myself) as a little excessive. Ideally, the starting voltage should be adjustable, as it is on some expensive controllers.

The +5 V requirement rarely causes an issue, even with "12 V" panels, but with solar panels that have a voltage close to battery voltage, especially "12 V" panel with a low Voc in hot conditions and batteries that are in a high state of charge, this can be a problem. It seems that is what happened in this case.

Overall MPPT controllers will deliver significantly more solar yield than PWM controllers even with a single "12 V" panel, but there are exceptions.

[Kelkara]

Originally Posted by noelex 77

Contrary to expectations, PWM controllers are better than MPPT controllers very early in the morning and late in the evening if the solar panel Vmp is reasonably close to the battery voltage. So your results are not surprising. This is because MPPT controllers have a high self consumption. Running all that complex circuitry and voltage conversion takes some energy.

I have wondered about this ... I suppose that would also apply to overcast conditions ... I have 220W of solar which is in excess of what I need in sunny conditions, but I am very grateful for the 1-2amp I can get with overcast skies... I don't really need more power in the sun, but want to maximise power under clouds. It sounds like I should stick with my PWM charger, and not "upgrade".

[s/v Jedi]

Originally Posted by wholybee

All I am getting from you is BS. If you can't explain it, you don't understand it. EE or not.

One thing is sure: he is not an EE.

[s/v Jedi]

Originally Posted by donradcliffe

Before we degenerate into chest thumping, I have a geek question.

If the PWM and MPPT controllers control charging by cutting the width of constant voltage pulses, and LiFePo4 battery life is affected by charging voltage, has anyone done a study on the effects of the PWM and MPPT on battery life? In other words, do those short 20v pulses damage your batteries?

I have a friend who is a VERY smart geek (he writes RV design and repair books), and after I convinced him to dump lead acid and go to LiFePo4, he put together a massive system for his RV which uses parallel panels mercury switches (like the really old solar controllers) to keep his bank charging between a cut in and cut out voltage. He's been running his system for a couple of years now, and loves the LiFePo4.

Cutting the width of pulses sounds like a description of PWM which means Pulse Width Modulation. Yes, this is what PWM controllers do, but not MPPT.

A MPPT controller changes its impedance value presented to the solar array and draws a graph to find at which value the most power is transferred. This is regardless of voltage and current. It also periodically tests this point of maximum power transfer to see if it has shifted.

The power that comes in is then fed to a battery charger that outputs exactly what the battery charge algorithm needs.

[s/v Jedi]

Originally Posted by Kelkara

I have wondered about this ... I suppose that would also apply to overcast conditions ... I have 220W of solar which is in excess of what I need in sunny conditions, but I am very grateful for the 1-2amp I can get with overcast skies... I don't really need more power in the sun, but want to maximise power under clouds. It sounds like I should stick with my PWM charger, and not "upgrade".

Is this a statement or a question? In short: no, MPPT will give you better performance as long as you have panels that accommodate it (much higher voltage than the batteries… I have 140V input from my solar array.

[Chotu]

Thankfully, a Jedi came in to save the day with his light saber of facts

That was good information.

in my case, due to shading from mast/boom i have a series/parallel, 4 panel array setup.

Since shade is invariably on port or starboard in most cases of shading, 2 panels on port have 1 mppt controller receiving the port high voltage and 2 panels on starboard have another mppt controller receiving starboard high voltage.

This way, shading of the boom (if any) doesn’t take the whole array power output down as it would if it were all in series and i retain the advantages of series higher voltage at the same time - ie: controllers come on at dawn

if fact, their relays wake me up in the morning and remind me to put the anchor light on at night. ha ha ha

Edit: sun has just dipped below the horizon and i can hear “click, click” of the relays disengaging. Time for anchor light

[noelex 77]

Originally Posted by Kelkara

I have wondered about this ... I suppose that would also apply to overcast conditions ... I have 220W of solar which is in excess of what I need in sunny conditions, but I am very grateful for the 1-2amp I can get with overcast skies... I don't really need more power in the sun, but want to maximise power under clouds. It sounds like I should stick with my PWM charger, and not "upgrade".

The light conditions have to be very poor before a PWM controller will exceed the performance of a MPPT controller even when the Vmp of the solar panels is not enormously higher than the battery voltage. These conditions do exist, such as dawn and dusk, but on average a MPPT controller will do better than a PWM controller unless your system is incorrectly designed.

The other issue is utilising the correct charging parameters. This is important for battery health. There are a small number PWM controllers with a wide range of adjustable parameters, but this premium feature is becoming increasingly hard to find in controllers that do not incorporate MPPT technology.

[s/v Jedi]

Originally Posted by Chotu

Thankfully, a Jedi came in to save the day with his light saber of facts

That was good information.

in my case, due to shading from mast/boom i have a series/parallel, 4 panel array setup.

Since shade is invariably on port or starboard in most cases of shading, 2 panels on port have 1 mppt controller receiving the port high voltage and 2 panels on starboard have another mppt controller receiving starboard high voltage.

This way, shading of the boom (if any) doesn’t take the whole array power output down as it would if it were all in series and i retain the advantages of series higher voltage at the same time - ie: controllers come on at dawn

if fact, their relays wake me up in the morning and remind me to put the anchor light on at night. ha ha ha

Edit: sun has just dipped below the horizon and i can hear “click, click” of the relays disengaging. Time for anchor light

If you have Victron MPPT then maybe it has a programmable relay that can switch the anchor light automatically

[Chotu]

Originally Posted by s/v Jedi

If you have Victron MPPT then maybe it has a programmable relay that can switch the anchor light automatically

Outback Flexmax 80s are my controllers.

they do have the same functionality actually!

[noelex 77]

Originally Posted by Chotu

Outback Flexmax 80s are my controllers.

they do have the same functionality actually!

Most of the better charge controllers have this feature, including the Outback 80.

On the Outback 80 look at the "night light" options in AUX mode to set this feature. It has been over a decade since I owned one of these controllers so you have to read the manual.

Automatic anchor lights can be a useful addition. However, the KISS approach is sometimes superior to setting up automated functions. Don’t include these options just because it is feasible, but rather when you feel that the added complexity is a worthwhile advantage.